This invention relates to an improved process of preparing carvedilol, as well as a new crystalline hydrate and solvate and forms of carvedilol, processes for the manufacture thereof, and pharmaceutical compositions thereof.
Carvedilol is a nonselective xcex2-adrenergic blocking agent with xcex11 blocking activity. Carvedilol, also known as (xc2x1)1-(9H-carbazol-4-yloxy)-3-[[2(2-methoxyphenoxy)ethyl]amino]-2-propanol, (CAS Registry No. 72956-09-3) has the structure of formula I. 
Carvedilol has a chiral center and can exist either as individual stereoisomers or in racemic form. Racemic carvedilol is the active ingredient of COREG(copyright), which is indicated for the treatment of congestive heart failure and hypertension. The nonselective xcex2-adrenergic activity of carvedilol is present in the S(xe2x88x92) enantiomer and the xcex11 blocking activity is present in both the R(+) and S(xe2x88x92) enantiomers at equal potency. Both the racemate and stereoisomers may be obtained according to procedures well known in the art (EP B 0127 099).
Synthesis of Carvedilol
U.S. Pat. No. 4,503,067, which is incorporated herein by reference, discloses a process of preparing carvedilol by the following reaction: 
in which 4-(oxiran-2-ylmethoxy)-9H-carbazole (formula II) is reacted with (2-(2-methoxyphenoxy)ethylamine (formula III) to form carvedilol (I). The above process produces a low yield of carvedilol at least in part because in addition to carvedilol, the process leads to the production of a bis impurity of the following structure (formula IV): 
(See EP 918055.)
In order to reduce the formation of the formula IV and to increase the yield of carvedilol, EP 918055 discloses using a benzyl protected form of the 2-(2-methoxyphenoxy)ethylamine (III).
Carvedilol Polymorphs
International application No. WO 99/05105, incorporated herein by reference, discloses that carvedilol can be isolated as two polymorphic forms, depending on the method of preparation. The two polymorphic forms, designated Form I and Form II, are reported to be monotropic and are distinguishable by their infrared, Raman and X-ray powder diffraction spectra. No evidence is found in the literature about the existence of hydrated solvate states of carvedilol.
Polymorphism is the property of some molecules and molecular complexes to assume more than one crystalline form in the solid state. A single molecule may give rise to a variety of crystal forms (also called xe2x80x9cpolymorphsxe2x80x9d, xe2x80x9chydratesxe2x80x9d or xe2x80x9csolvatesxe2x80x9d) having distinct physical properties. For a general review of polymorphs and the pharmaceutical applications of polymorphs see G. M. Wall, Pharm Manuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, J. Pharm. Sci., 58, 911 (1969); and J. K. Haleblian, J. Pharm. Sci., 64, 1269 (1975), all of which are incorporated herein by reference.
The existence and physical properties of different crystal forms can be determined by a variety of techniques such as X-ray diffraction spectroscopy, differential scanning calorimetry and infrared spectroscopy. Differences in the physical properties of different crystal forms result from the orientation and intermolecular interactions of adjacent molecules (complexes) in the bulk solid. Accordingly, polymorphs, hydrates and solvates are distinct solids sharing the same molecular formula yet having distinct advantageous and/or disadvantageous physical properties compared to other forms in the polymorph family. The existence and physical properties of polymorphs, hydrates and solvates is unpredictable.
One of the most important physical properties of a pharmaceutical compound which can form polymorphs, hydrates or solvates, is its solubility in aqueous solution, particularly the solubility in gastric juices of a patient. Other important properties relate to the ease of processing the form into pharmaceutical dosages, such as the tendency of a powdered or granulated form to flow and the surface properties that determine whether crystals of the form will adhere to each other when compacted into a tablet.
The present invention provides a process for preparing carvedilol comprising a step of reacting a compound of formula II, 4-(oxiran-2-ylmethoxy)-9H-carbazole, 
with a compound of formula III, 2-(2-methoxyphenoxy)ethylamine 
wherein the compound of formula III is at a molar excess over the compound of formula II.
The present invention further provides crystalline carvedilol hydrate.
The present invention further provides crystalline carvedilol.
The present invention further provides crystalline carvedilol (methyl-ethyl-ketone) solvate.
The present invention further provides crystalline carvedilol Form III characterized by an X-ray powder diffraction pattern having peaks at about 8.4xc2x10.2, 17.4xc2x10.2, and 22.0xc2x10.2 degrees two-theta.
The present invention further provides crystalline carvedilol Form IV characterized by an X-ray powder diffraction pattern having peaks at about 11.9xc2x10.2, 14.2xc2x10.2, 18.3xc2x10.2, 19.2xc2x10.2, 21.7xc2x10.2, and 24.2xc2x10.2 degrees two-theta.
The present invention further provides crystalline carvedilol (methyl-ethyl-ketone) solvate Form V characterized by an X-ray powder diffraction pattern having peaks at about 4.1xc2x10.2, 10.3xc2x10.2, and 10.7xc2x10.2 degrees two-theta.
The present invention further provides carvedilol HCl Hydrate characterized by an X-ray powder diffraction pattern having peaks at about 6.5xc2x10.2, 10.2xc2x10.2, 10.4xc2x10.2, 15.8xc2x10.2, 16.4xc2x10.2 and 22.2xc2x10.2 degrees two-theta.
The present invention further provides a method for preparing crystalline carvedilol Form I, comprising the steps of dissolving carvedilol in a solution by heating; heating the solution until the crystalline carvedilol is completely dissolved; reducing the temperature of the solution; agitating the solution for a period of time; further reducing the temperature of the solution; further agitating the solution for a period of time; and collecting crystalline carvedilol Form I.
The present invention further provides a method for preparing crystalline carvedilol Form II, comprising the steps of forming a solution of carvedilol by dissolving carvedilol in a solvent; precipitating carvedilol Form II by cooling the solution; and, isolating crystalline carvedilol Form II.
The present invention further provides a method for preparing crystalline carvedilol Form II, comprising the steps of forming a solution of carvedilol by dissolving carvedilol in a solvent mixture; precipitating carvedilol Form II by cooling the solution to about xe2x88x9220xc2x0 C.; and, isolating crystalline carvedilol Form II.
The present invention further provides a method for preparing crystalline carvedilol Form III, comprising the steps of dissolving carvedilol in a solvent to form a solvent solution; and, precipitating crystalline carvedilol Form III from the solvent solution using water as an anti-solvent.
The present invention further provides a method for preparing crystalline carvedilol Form III, comprising the steps of dissolving carvedilol in a solution by heating; cooling the solution mixture; and, collecting crystalline carvedilol Form III.
The present invention further provides a method for preparing crystalline carvedilol Form IV, comprising the steps of dissolving carvedilol in a solvent to form a solvent solution; adding an anti-solvent to the solvent solution; and, precipitating crystalline carvedilol Form IV from the solvent solution.
The present invention further provides a method for preparing crystalline carvedilol Form V, comprising the steps of dissolving carvedilol in a solvent to form a solvent solution; and, precipitating and isolating crystalline carvedilol Form V from the solvent solution.
The present invention further provides a method for preparing crystalline carvedilol Form V, comprising the steps of dissolving carvedilol in a solvent to form a solvent solution; and, precipitating and isolating crystalline carvedilol Form V from the solvent solution wherein the precipitation step is performed by adding an anti-solvent.